Hydrogen is universally considered a fuel of the future due to environmental advantages over conventional (i.e., fossil-based) fuels. Another important advantage of using hydrogen stems from the fact that it could be electrochemically (i.e., without Carnot-cycle limitation) converted into electricity with very high energy conversion efficiency using fuel cells (FC).
To be used in energy conversion devices, hydrogen has to be produced and stored; however, each of these aspects of hydrogen technology is associated with major technological challenges. Conventional (non-electrolytic) hydrogen production processes (for example, steam methane reforming) are complex, multi-stage devices that produce significant amounts of carbon dioxide (CO2) emissions at the production site and, besides, are very difficult to down-scale (e.g., to sub-kilowatt range). Hydrogen storage is another major roadblock to a widespread use of hydrogen in power generation systems. Conventional hydrogen storage systems in the form of a compressed gas, or a liquid, or a metal hydride, suffer from either low gravimetric and volumetric densities, or high cost, or safety-related problems, and the like.
Various methods for generating or producing hydrogen based on the reactions of metal hydrides or metals or their alloys with water are known and are referenced below.
S. Amendola et al. in U.S. Pat. No. 6,534,033 B1 describes a system for hydrogen generation, and in U.S. Pat. No. 6,683,025 B2 describes a process for making hydrogen generation catalysts. Both patents involve a method for storage and controlled release of hydrogen via use of sodium borohydride-based solutions and a catalytic system. Patent Cooperation Treaty (PCT) publication, WO 2004/035,464 to R. Chen describes hydrogen generation apparatus in which a hydride (stabilized NaBH4) is decomposed by a catalyst to produce hydrogen and waste products.
Methods for producing hydrogen using aluminum and water are disclosed in U.S. Pat. No. 6,506,360 B1 to Andersen et al., PCT publication WO 2002/08118 01 to Andersen et al. entitled, “Hydrogen production from aluminum, water and sodium hydroxide,” US Patent Appl. Publ. 2003/0143155 to Andersen et al.; PCT publication WO 2004/052775 to Andersen et al. entitled, “Method for producing hydrogen from aluminum”, U.S. Patent Appl. Publ. 2004/0115125 to E. R. Andersen et al. entitled, “Renewable energy carrier system and method.” A method and an apparatus for producing hydrogen include reacting aluminum with water in the presence of NaOH as a catalyst. The reaction vessel contains 0.26-19 M aqueous solution of NaOH.
PCT publication WO 02/06153 A1 to E. Baldwin et al. discloses a method of contacting an aqueous liquid (alkali metal hydroxide) with a dissociation initiating material (Al or Na—Al alloys) in a reaction vessel and controlling the surface area of dissociation and pressure therein.
PCT publication WO 2002/14213 A2, to A. Chaklader, et al. discloses a method for producing hydrogen by reacting a metal selected from Al, Mg, Si, Zn with water in the presence of a catalyst at pH between 4 and 10.
U.S. Patent Application Publ. US 2004/0018145 Al, to T. Suzuki et al. discloses a method wherein water and MgH2 react to produce target high-pressure hydrogen in a high-pressure container.
A Japanese patent JP 62263946 to H. Kudo et al. describes the use of quenched aluminum-bismuth alloy for hydrogen production wherein Al—Bi alloy (solidified at >104° C./s) produced hydrogen by dipping in 70° C. water.
A Soviet Union patent, SU 945061 (1982) to L. Kozin et al. disclosed an aluminum-based composition for preparing hydrogen; Al—Hg (3-5 wt. %) alloy was used to produce hydrogen from water.
K. Scherbina in “Solid-phase reaction products in hydrogen generation processes,” Problemy Mashinostroeniya (1983), v. 20, pp. 83-86 (in Russian) reports that hydrogen was produced by decomposition of water with Al—Li (16%), Al—Li (50%), Al—Na (50%) composites.
Another Soviet Union patent, SU1675199 (1991) to M. Khazin et al. describes the use of aluminum-iron-silicon alloy for producing hydrogen by decomposition of water. The alloy for the efficient production of hydrogen contains Ca (0.1-1%), Na (0.01-1%), Cu (0.1-3%), Fe(5-15%), the balance-Si.
Additional methods for producing hydrogen and heat energy are disclosed by A. Yelkin et al. in PCT publications WO 2003/104344 and WO 2002/14214 A1. The methods consist of preparing a composition based on activated textured aluminum or Al-containing material and reacting it with water. The activation of Al is carried out by means of applying molten fusible metals with low melting point (Ga, Sn, In) to the end surface of Al.
G. Antonini et al. in “Hydrogen generation from concentrated aluminum-water suspensions. Application for continuous heat production by catalytic combustion.” Recents Progres en Genie des Procedes (1991) 5 (16) pp. 81-86. A process was developed for chemical storage of hydrogen as concentrated suspensions of Al powder in H2O/NaOH. The suspension can be made to produce hydrogen on demand. Hot water for the reaction is taken from a boiler where catalytic combustion of hydrogen is carried out.
M. Matsuyama et al. in “Hydrogen production from water using waste aluminum.” Toyama Daigaku Suiso Doitai Kino Kenkyu Senta Hokoku (1992) 12, pp. 49-58 discusses factors affecting the rate of hydrogen production from water using Al and Al—Mg alloys were investigated.
In British patent GB 2344110 to G. Carloss, the production of alloy granules for hydrogen generation is discussed. The granules are made from Al, Sn, Zn and trace amounts of Si and Sb. The granules react with hot water with the production of hydrogen gas.
Hydrogen generation is observed in the wet cutting of Al and its alloys due to the reaction between the fresh surface of Al with water as reported by K. Uehara et al. in “Hydrogen gas generation in the wet cutting of aluminum and its alloys” J. Mater. Proc. Techn. (2002) 127, pp. 174-177.
Aluminum samples in the form of a cylindrical block, powder or pellets react with aqueous solutions of NaOH to generate hydrogen gas are discussed by D. Belitskus, in “Reaction of aluminum with sodium hydroxide solution as a source of hydrogen,” J. Electrochem. Soc. (1970) 117, pp. 1097-1099.
It should be noted, however, that the systems based on metal hydrides, and particularly complex metal hydrides, are rather costly and require preliminary preparation of reacting solutions and the use of expensive noble metal based catalysts. Metal-based systems also suffer from a number of shortcomings. Metals or alloys, such as, Li, Na, K, Ca, Al—Hg, Al—Li, Al—Na, Si—Al—Ca—Na—Fe—Cu, that directly react with water at ambient temperature are either expensive, or hazardous, or present great safety concerns, including, violent uncontrolled reaction with water. On the other hand, such inexpensive and readily available materials like aluminum (Al) and its alloys and iron (Fe) and its alloys do not react with water at ambient temperature. Al can release hydrogen from aqueous solutions only in the presence of substances, such as, alkali hydroxides: NaOH, KOH, that remove a protective oxide layer from Al surface and, as a result, are consumed in the process, since they are transformed into respective aluminates.
Thus, there is a need for an efficient, simple and inexpensive hydrogen-generating system and a device that could be easily adopted to different capacities from watts to kilowatt range. There is also a need for a method and an apparatus to safely produce hydrogen using water and other readily available materials in locations where it may be conveniently used for heat and/or electricity generation. There is also a need for more efficient chemical compositions that exceed the performance characteristics, such as, specific energy, power density, of the state-of-the-art hydrogen-generating systems.
The present invention improves upon the deficiencies of the prior art which include, but are not limited to, the following.
The disclosed system has greater power density (i.e., amount of hydrogen produced from unit of weight or volume of the reagents used) compared to prior art. The present invention is simpler and more compact. Hydrogen is produced directly from water, not from reacting solutions of water-soluble hydrides as in prior art. Hydrogen production starts immediately upon the addition of water without any induction or warming-up period. The present invention utilizes inexpensive readily available reagents and catalysts.